Unfortunately, bash shows up in surprising places, including default Solaris installs nowadays.
On OSX and Solaris, I've chmod'ed 0000 /bin/bash with no apparent ill effect so far. I'll put more effort into establishing its acceptability as a solution tomorrow.
BSDs won't have bash unless someone has gone out of their way to install it, which can be undone straightforwardly.
But it could be a long night for our Linux brethren and sistren.
Good luck, and remember to stay hydrated. :)
EDIT: obviously, don't chmod 0000 your login shell! Fix that first. Make sure whatever you switch to isn't a symbolic or hard link to bash.
